Historically most refrigerants have had "issues" when leaked either environmental or being toxic or otherwise it minimizes danger to keep as little as possible. Even if we could afford to use 1000x as much refrigerant with a central compressor station, it would be bad for the environment to use it that way.
You can move a huge amount of heat with water pressurized to merely 14 psi or so, but I have a puron aka R-410A conditioner at home and that dude runs near 400 psi on a hot day and its difficult to run miles of high pressure pipe.
I'm not sure bigger compressors are that much more efficient than smaller compressors, taking into account the environmental and economic expense of the pipes.
From an engineering standpoint its cheaper safer and less environmentally destructive to push kilowatts thru copper wire than push high pressure expensive refrigerant thru long high pressure pipes if all other things were equal which they mostly are.
For a long while, Stanford had an underground reservoir of ice for even better cooling (freeze ice at night when electrical prices are low, melt off during the day) http://web.stanford.edu/dept/news/news/1999/april21/iceplant...
The heat version of it is very common here in Sweden (for towns bigger than, say, 10k people) and it is a lot more efficient (and therefore, cheaper) than having heating units in the different buildings. We even have bigger data centers selling their spare heat from their cooling back to the heating systems.
Very large building-sized boiler and chiller plants served each half of my campus (probably less than a square mile in total). I'm not sure it would work at city scale.